US1996838A - Method of and means for bending tubes - Google Patents

Description

April 9, 1935.

L. W. SNELL METHOD OF AND MEANS FOR BENDING TUBES 2 sheets-sheet 1 Filed July 25, 1952 /NVENTOR 1 L. w- S/vl. L. 5v NCQ@ nrro e/vzn Y April 9,1935. j LfwsN'ELL 1,996,838

n METHOD OF AND MEANS FOR BENDING TUBES Filed July 25, 1932 2 sheets-sheei 2 Patented Apr. 9, 1935 UNITED STATES PATENT OFFICE 1,996,833 METHOD oF AND MEANS Eon BENDING TUBES p Lester W. Snell, Alton, lll. Application July 25, 1932, Serial No. 624,405 17 Claims. (Cl. 153-32) This invention relates to methods of and means i for bending tubes, and the novel features may such as U-shaped return bends, elbows with end portions at various angles to each other, and also` v in making long continuous coils of tubing.

In performing an ordinary simple bending operation, a metal tube is stretched at the arc oi' greatest radius which is termed the outer portion of the bend, while the metal is compressed at the' inner portion of the bend, where the radius of the curve is shorter. The stretching in this old method reduces the thickness of the metal at the outer portion of the bend, while the compression increases the thickness at the inner portion of the bend. As a consequence, the ordinary simple bending operation results in a bent tube that is non-uniform in thickness.

One of the objects of this invention is tobend the tubes while preventing undesirable variations in the thickness of the tube walls.

Another object is to accurately bend the tubes to a predetermined curvature and diameter.

A further object is to provide the bent tube with a smooth and uniform circular outer face.

With the foregoing and other objects in view, the invention comprises the novel method, construction, combination and arrangement of parts hereinafter more specifically described and illustrated in the accompanying drawings, wherein is shown the preferred embodiment of the invention. However, it is to be understood that the invention comprehends changes, variations `and modifications which come within the scopeof the claims hereunto appended.

Fig. 1 is a section illustrating a bending system embodying the features of this invention.

Fig. 2 is a transverse section on the line 2 2 in Fig. 1, showing variations in the thickness of the tube to be bent.

Fig. 3 is a section on the line 3 3 in Fig. 1, showing the uniform thickness of the bents tube.

` Fig. 4 is a section on the line 4 4 in Fig. 1.

I Fig. 5 is a section on the line 5 5 in Fig. 1.

Fig. 6 is a side elevation on a smaller scale showing a hammer-operating device.

Fig. 7 is a section taken approximately on the line 1 1 in Fig. 6.

Fig. 8 is a section taken approximately on the line 8 8 in Fig. 6. l

'Ihe apparatus shown `'to illustrate one form of the invention comprises a forming die 9 made of two sections contacting with each other at the line I0 in Fig. 5, and alinedl by means of dowel pins I I, saicl die having a curved passageway I2,

through which the tube to give the desired curvature.

I3 indicates a tube adapted to be forced through the passageway I2. In the preferred form of theinvention, the 4first step comprises 6 forming a continuous straight tube of any desired length of a cross section, such as shown by Fig. 2. This straight tube has a relatively thick portion which extends longitudinally of the tube, and the thickness gradually decreases circumferentially l0 to a point' diametrically opposite said thick portion.

In other words, as shown in Fig. 2, the thick portion of the tube to be bent lies directly opposite the thin portion, and there is a gradual 16 be bent is forced to change in thickness between these portions,.the

inner face of the tube being eccentric to the outer face. After the tube has been forced through the curved passageway I2, it is curved as shown at the left of Fig. 1, and it has a uniform thick- 20 ness, as shown in Fig. 3. 'I'his uniformity in thickness of the bent tube is due partly to the non-uniformity in thickness of the material to bepbent, and partly to the upsetting operation which occurs when the tube is bent.

Il designates a stationary guide tube (Fig. 1) extending from the entrance of the curved passageway I2 and conforming to the outer face of the straight portion of the tube I3. A heating chamber I5 surrounding the guide tube I4 may be 30 covered with insulation I Ii and provided with inlet and exhaust pipes I'l and I8 for the admission and discharge-of the heating medium, which may be a highly heated gas or other suitable heating agent. 'Ihe heat transmitted from this 35 chamber I5 may be great enough to, subject the tube I3 to a substantially uniform red heat while it passes through the guide tube I4.

The thickest portion of the tube I3 passes from the guide tube I4 to the curve of largest radius in 40 the curved passageway I2, as shown in Fig. 1, while the thinnest portion in said tube passes through the curve of shortest radius in said pas- Sageway.

The tube la may be pushed through the giuda, 45 I4 by any suitable power and is gradually heated to a uniform high temperature by the heat transmitted from the surrounding chamber I5.'

A local cooler I9 is located at the entrance to the` 50 curved passageway I2 so that the thickest portion of the tube to be bent is subjected to a Acooling action as it passes to the bending zone in the curved passageway I2. Y

As shown by Fig. 4, the local cooler Il may be I6 hammer is smaller than yment from the arms provided with inlet and discharge pipes 28 and 2| through which a cooling fluid is transmitted.

The bending zone in the curved passageway I2 extends approximately from the entrance of said passageway to a position near the point designated by 22. The curved passageway is preferably tapered as suggested by dimensions appearing in Fig. 1. It is larger in diameter at the bending zone than the diameter of the tube to be bent, and slightly smaller in diameter beyond the bending zone than the diameter of the passageway at the bending zone.

The decrease in diameter of the passageway I2 beyond the bending zone will eliminate the slight flattening which occurs at the inner arc of the tube where the pressure tends to force the tube away from the face of the die, and this feature also provides the tube with a smooth and uniform circular outer face.

A hammer 23 having a curved portion 24 is located in the curved passageway I2. i The hammer is provided with a straight portion 25 extending into the straight passageway I4. The diameter of the straight portion 25 of the hammer is approximately equal to the internal diameter of the tube to be bent, and the curved portion 24 of said the internal diameter of the tube as it passes the curved portion of the hammer.

In the drawings I have shown a device for reciprocating the hammer in the passageways I2 and I4. However, it is to be understood that any other suitable means could be used to operate the hammer. l f e The device as shown comprises a rod 26 having a head 21 which is located in a chamber 28 in the straight portion 25 of the hammer, as shown in Fig. 1. The head 21 on the rod 26 is adapted to strike the walls 29. and 30 of the chamber 28 to force the hammer backward and forward in the passageways I2 and I4.

The rearward portion of the rod 26 is adapted to receive arms 3| which are pivotally secured to a shaft 32 and held in position by the collars 33. The lower portions of the arms 3| are in the form of hooks 34and, as shown in Fig. 1, these hooks are detachably secured to the rod 26. Collars 35 are located on the rod 26 at opposite sides of the arms 3l to provide for the transmission of move- 3| to said rod 26.

The shaft 32 is slidably supported in hangers 36- and 31. A spring 38 is located on the shaft between the hanger 31 and a spring seat 38. This spring will tend to hold the shaft 32 and rod 26 in their rearwardpositions.

To provide for the reciprocation of the shaft 32 and rod 26, I have shown bevel gears 48 and 4I through whichpower is transmitted from a motor 42 to a carn.43. A collar 44 which is secured to the shaft 32 by a set screw 45, has a projection 46 which lies in the path of the cam 43. As the cam 43 rotates, the extended portion 41 of the cam will force the projection 46 on the collar together with the shaft 32 and rod 26 forwardly, and after the extended portion o'f the cam passes the projection 46 on the collar, the spring 38 will force the shaft 32 and rod 26 to a rearwardposition. Since the hammer 23 is operatively secured vto the lrod 26, it will likewise be reciprocated by the cam 43 and spring 36.

The curved portion 24 of the hammer (Fig. l) is provided with a curved face 48 conforming to the curvature of the inner face of the arc of relatively large radius of the bent tube.

`way I in the rod The curved portion 24V of the hammer is also provided with another curved face 49 conforming to the curvature of the inner face of the arc of relatively small radius of the bent tube.

The curved face 48 of the hammer provides a cam which forces the tube onto the curve of largest radius in the curved passageway at the completion of the forward stroke of the hammer, and at the same time forces a portion of the hammer in the straight passageway onto the portion of the tube approaching the bending zone at the are of smallest radius.

The curved face 49 of the hammer provides a cam which forces the tube onto the curve'of smallest radius in the curved passageway at the completion of the rearward stroke of the hammer, and at the same time forces a portion of the hammer in the straight passageway onto the portion of the tube approaching the bending zone at the arc of largest radius.

shown a passageway 50 extending from the chamber 28 in the hammer to the forward end of the hammer. The rod 26 has a passageway 5|, and

the head 21 on said rod is provided with passageways 52 which communicate with the passageway 5| and the chamber 28. Air or other cooling medium may, therefore, be forced from any suitable source (not shown) through the passage- 26, and through the passageways 52, chamber 28 and passageway 58 to provide the desired cooling of the hammer.

The chamber 28 in the straight portion of the hammer is preferably surrounded by insulation 53 to retard the transmission of heat from the heating chamber I5 to the chamber 28 where the head 21 on the rod 26 strikes the walls 29 and 30.

The operation of the parts so far described will be briefly set forth as follows:

The arms 3| are detached from the shaft 32 and a tube I3 having an external diameter of 3.392 and a cross section, suchas shown in Fig. 2, may be placed onto the rod 26. The arms 3| are then replaced in position and the tube forced by any suitable means (not shown) through the straight passageway I4 and the curved passageway I2.

Additional tubes I3 may be delivered to the apparatus, as shown by dotted lines in Fig. 6, and the bending operations may be carried out continuously for an' indefinite period. Each tube, excepting the rst, pushes a. preceding tube entirely through the bending die, and the bent tubes are discharged from the apparatus in the form of elbows, return bends, or the like, depending upon the length of the straight tube sections delivered to r.the apparatus.

When the tube passes through the straight passageway I4, it may be heated to a substantially uniform red heat by the heat transmitted from the heating chamber I5. As the tube passes to the bending zone, the thickest portion of the tube is subjected to a cooling action at the local cooler I9 to prevent substantial upsetting of the relatively thick portion of the tube in the bending zone.

When the tube enters the bending zone it is preferably enlarged so that it will have an externaldiameter slightly greater than 3.5 inches.

When the tube is forced through the bending zone of the curved passageway I2, it has a tendency to' depart -from the arcuate faces of the To prevent overheating of the hammer, I have to produce a bridging action `and thus separate the tube from the inner arc of the curved passageway.`v

The hammer 23 is reciprocated while the tube is passing through the bending zone. When the hammer reaches the end of its forward stroke, its curved face 48 will strike the tube on its inner face at the arc of relatively large radius and force this portion of the tube onto the relatively large arc of the curved passageway.

The curved face 48 of the hammer will also provide a cam action on the face of the tube,

to force the straightportion 25 of the hammer onto the' thin portion of the tube to p'revent buckling of the relatively hot thin metal approaching the bending zone.

After the completion of the forward stroke of the hammer 23, the curved face 48 of the hammer will remain in contact with the inner face of the tube while the head 21 on the rod 28 travels from the wall 29 of the chamber 28 to the wall 39. This period of time, however, is relatively short as the spring 38 immediately withdraws the rod 28 when the extended portionof the cam 4,3 passes the projection 46 on theV collar 44.

At the completion of the rearward stroke of the hammer 23, the curved face 49 of the hammer will force metal of the tube at the curve of small radius onto the face of the curved passageway having a relatively small radius, to prevent any bridging action which might separate the tube from 'the inner or relatively small arc of the die.

The curved face 49 of the hammer 23 will at this time provide a cam action against the inner face of the tube at the arc of relatively small radius to force the straight portion 25 of the hammer onto the thick straight portion of thev tube to prevent irregular 'separation of this portion of the tube from the wall of the straight passageway.

After the completion ofthe rearward stroke of the hammer there is a relatively long time interval during whichthe curved; face 49 of the-hammer remains ln. contact with the tube. This interval is due` .to the fact that the cam must travel a relatively long distancebefore it again forces the hammer forward.

" 'I'he curved faces 48 and 49 of the hammer conV- form vto the curvatures desired y,in the bending v, zone. The inner faces of the tuberat the relativelylarge and small arcs wil1therefore, be given the desired curvature duringthe 'hammer-v ing actionin the bending zone. f In theform of the invention; disclosed wherein the/tube is `enlarged:inthe bendingzone,A the curved portion-24 .of the reciprocating. hammerl will. aid in ,enlarging theD tube by ,i'orcvirng". Vit V ontathewalls of. the curvedmssewy- After Ythe .tube passes l.from .the bending... zone it isslightly contracter,igtoa.diameterfofy approxi-. mately-inchesfin thecurved-passageway i2` to.. insure a smooth and; uniform circular outerl face. lWhen the-tubeias .illwitrated*inlilies-.11.y .and passes tromfthef. die. .-the=.-w11s fit-they tube;.w1li here a uniform thicknessofpnrasmately02.16, an external diame r,of3`.f5 yand van internaidh,

form ofmy invention, andthey ydoritin 'any lway-.3V

1. The' mattei attaquent aived* tutti" tube while forcing the same through a curved passageway, hammering the inner face of the arc of relatively large radius of the tube `during said bending operation to force the tube onto the curved face 'of the largest radius in said passageway, and hammering the inner face of the arc of relatively small radius of the` tube during said bending operation to force the tube onto the curved face of smaller radius in said passageway. 2. 'Ihe method of producing curved tubes which comprises heating a tube, bending said tube and enlarging the diameter thereof while forcing said tube through a curved passageway, hammering the inner face of the arc of relatively large radius of the tube during said bending operation to force the tube onto the face of largest radius in said passageway, hammering the inner face of the arc of relatively small radius of the tube during said bending operation to force the tube onto the curved face of smaller radius in said passageway to prevent a bridging action of the material at the curve of smallest radius, and to aid in enlarging the diameter of the tube, cooling the relatively thick portion of the tube to check an upsetting action in said thick portion,` and then slightly contracting said tube to provide the tube with va substantially smooth and uniform circular outer face.

3. 'I'he method of producing curved tubes which comprises forming a tube with a relatively thick portion longitudinally of thetube, the thickness decreasing circumferentially to a. point dia metrically opposite said thick portion, heating said tube, bending said tube and enlarging the diameter thereof by forcing said tube. through a curved passageway, and hammeringD the arcs of relatively large and small radii of the tube during said bending operation. I

4. 'Ihe method of producing curved tubes which comprises forming a tube with a relatively thick portion longitudinally ofthe tube, the thickness decreasing circumferentially to a point diametrically opposite said thick portion, heating said A said bending operation to force the tube onto the 4 curve of largest radius in said curvedpassageway, hammering the inner face of the arc of relatively small radius of the tube during said bending operation lto-vforce the tube onto the curve of smaller radius in said passageway, to prevent a bridging actionof the tube at the curve of smallest radius and to aid in enlarging the Idiameter of the tube, cooling the relatively thick portion of the tube duringsaid bending operation to check an upfsetting, action in said thick portion, and then slightly contracting the diameter of the bent tube to provide the tube with a substantially smooth and runiform circular outer face.

, 5l `In vartube bending. apparatus, a bending die having acurved passageway through which the tube. is forced to form the desired bend, said curved passageway having a larger diameter at thefbending zone than the diameter of the tube tafbe,v bent, so as to enlarge the tube during the bending operation, and means whereby the tube is j-forced yentirely throughand discharged from saidcurved passageway.

`6...In. a..tube bending apparatus, a bending die having a curved passageway through which the tube is forced to form the desired bend, a curved hammer secured within said passageway so as to remain at the bending zone therein, and means whereby said hammer is forced onto the inner face of the bend of largest radius of the tube to forcethe tube onto the arc of largest radius of the curved passageway.

7. In a tube bending apparatus, a bending die having a curved passageway through which the tube is forced to form the desired bend, a curved hammer secured within said passageway so as to remain at,the bending zone therein, and means whereby said hammer is forced onto the inner face of the bend of relatively small radius in the tube to force the tube onto the corresponding portion of the curved passageway.

8. In a tube bending apparatus, a bending die having a curved passageway through which the tube is forced to form the desired bend, a hammer secured in said passageway so as to remain at the bending zone therein, and means whereby said hammer is reciprocated to alternately "force the tube onto oppositely disposed faces of said curved passageway. Y

9. In a tube bending-apparatus, a bending die having a curved passageway through which the tube is forced to form the desired bend, said curved passageway having a larger diameter at the bending zone than the diameter of the tube to be bent, said curved passageway being 'slightly smaller in diameter beyond the bending zone ythan the diameter. of the passageway at the bending zone, a curved hammer located in said curved passageway, said curved hammer being smaller in diameter than the internal diameter of the tube passing the curved portion of the hammer, and means whereby said hammerI is reciprocated in said passageway, said curved hammer providing a cam face adapted to force the tube onto the curve of largest radius in the curved passage- .way at the completion of one stroke of the hammer, said `curved hammer also providing a cam face adapted to force the tube onto the curve of small radius in the curved passageway at the completion of another stroke of the hammer.

10. In a tube bending apparatus, a bending die having a curved passageway through which the tube is forced to form the desired bend, a cylindrical housing communicating with said curved passageway, said cylindrical housing having a straight passageway conforming to the external diameter of the tube to be bent, a hammer having a curved portion located in said curved passageway, said hammer being provided with a straight portion extending into said straight passageway, the diameter of said straight portion of the hammer being approximately equal to the internal diameter of the tube to be bent, the curved portion of said hammer being smaller in diameter than the internal diameter of the tube passing the curved portion of the hammer, and means whereby said hammer is reciprocated in said passageways, said curved hammer providing a cam face adapted to force the tube onto the curve of largest radius in the curved passageway at the completion of the forward stroke of the hammer while forcing a portion of the hammer in the straight passageway onto the portion of the tube approaching the bending zone at the arc of smallest radius, said curved hammer also providing a cam face adapted to force the tube onto the curve offrelatively small radius in the curved passageway while forcing a portion of the hammerin the straight passageway onto the portion of the tube approaching the bending zone at the are of largest radius. I

11. Ina tube bending apparatus, a bending die disposed faces of said curved passageway.

vhaving a curved passageway through which the tube is forced to form the desired bend, a cylindrical housing communicating with said -to be bent, said curved passageway being slightly smaller in diameter beyond the bending zone than the diameter of the passageway-at the bending zone, a hammer having a curved portion located in said curved passageway, said hammer being provided with a straight portion extending into said straight passageway, the diameter of said straight portion of the hammer being approximately equal to the internal diameter of the tube to be bent, the curved portion of said hammer being smaller in diameter than the internal diameterof the tube passing the curved portion of the hammer, and means -whereby said hammer is reciprocated in said passageways, said curved portion of the hammer including a cam face adapted to force the tube onto the curve of largest radius in the curved passageway at the completion of the forward stroke of the hammer while forcing av portion of the hammer in the straightpassageway at the completion of the rearward stroke of the hammer and to force a portion of the hammer in the straight passageway onto the portion of the tube approaching the bending zone at the arc of largest radius.

12. The ,method of producing curved tubes which comprises bending a traveling tube while forcing successive portions of said tube entirely through a curved bending zone to form a curved bend in the tube, and at the same time forcibly smoothing successive portions of the curved bend by transmitting them from said curved bending zone, through a correspondingly curved contracting zone and forcibly reducing the diameter of said curved bend as it travels through said curved contracting zone, said curved bend being transmitted entirely through said curved contracting zone to produce ,a curved tube having a substantially smooth and uniform outer face.

13. 'I'he method of producing curved tubes which comprises bending and increasing the diameter of a traveling tube while forcing successive portions of said tube entirely through a curved bending zoneC to. form a curved bend in the tube, and at the same time forcibly smoothing successive portions of the curved bend by transmitting them from said vcurved* bending zone, through a correspondingly curved contracting zone and forcibly reducing the diameter of said curved bend as it travels through said curved contracting zone, said curved bend being transmitted entirely through said curved contracting zone to produce a curved tube having a substantially smooth and uniform outer face.

14. The method of producing curved tubes which comprises bending a tube by forcing it through a curvedpassageway, and 'continually hammering the inner face of the tube during the bending operation by striking hammer blows on the curves of relatively large and small radii formed in the bent portions of the tube, so as to hammer said bent portions onto the opposltely l 1,996,838 15. The method of producing curved tubesv which comprises bending a tube by forcing it entirely through a curved passageway, and continually hammering the inner face of the tube by striking alternate hammer blows on the curves of relatively large and small radii formed in the -oppositely disposed bent portions of the tube, so-

as to alternately hammer said bent portions onto the oppositely disposed faces of said curved passageway.

16. In a tube-bendingapparatus, a bending die having a curved passageway including an arcuate bending zone into which the tube is forced to form a correspondingly curved bend and an arcuate contracting zone through which the curved bend is discharged, said curved passageway-being contracted beyond said bending zone to reduce the diameter of the curved bend as it passes through said arcuate contracting zone.

17. In a tube-bending apparatus, a bending die having a curved passageway including an arcuate bending zone into which the tube is forced to form a correspondingly curved bend and an arcuate contracting zone through. which the curved bend is discharged, the diameter of the bending zone in said curved passagewayV being larger than the diameter of the tube to be bent, and said curved passageway being contracted beyond said bending zone to reduce the diameter of the curved bend as it passes through said arcuate contracting zone.

LESTER Wr SNELL.

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